Polyaryletherketones (PAEKs) are a family of high-performance thermoplastics with a highly aromatic backbone connected by ketone groups and ether linkages. They exhibit high thermal stability, chemical resistance, and high mechanical strength. Due to their restricted chain motions, PAEKs display higher crystallinity, glass transition temperatures (Tg), and melting points (Tm) compared to other thermoplastics. However, they are insoluble in many organic solvents, such that their study and characterization are mostly carried out in strongly acidic solutions such as sulfuric and trifluoroacetic acid. It is hypothesized that introducing geminal methyl groups into the backbone of PAEKs, such as polyetherketoneketones (PEKKs), can result in improved processability with some organic solvents without compromising their thermal performance. In this work, Friedel-Crafts polymerization of PEKK copolymers was performed using comonomers of terephthaloyl chloride, diphenyl ether, and dimethyl malonyl chloride in varying proportions. The synthesized copolymers were characterized by NMR, FT-IR spectroscopy, GPC, TGA, XRD, and DSC. Results showed that varying the stoichiometric ratios of the comonomers can tune the thermal performance and solubility of the resultant copolymers. The thermal properties of the prepared PEKK copolymers were also compared with PEKKs having unmodified backbones.

Friedel-Crafts polycondensation of diphenyl ether and commercial diacyl chloride monomers toward Versatile polyetherketoneketones (PEKKs)

ACS Fall 2021

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